/Engine/Source/Runtime/Engine/Public/ShaderCompiler.h
https://docs.unrealengine.com/latest/INT/Programming/UnrealArchitecture/StringHandling/FString/
void RegisterCompiledShaders ( uint32 NumPermutations, EShaderPlatform Platform, const [FString](API\Runtime\Core\Containers\FString) MaterialPath, [FString](API\Runtime\Core\Containers\FString) PermutationString )